644 THE BIOCHEMISTRY OF B VITAMINS 



pantothenic acid-deficient diet. Administration of an adequate amount of 

 pantothenic acid prevented or cured the deficiency disease caused by the 

 analogue. Strain differences in mice were observed, and graying of fur was 

 noted in only one of five experimental groups. 



Analogues of Pantothenic Acid Modified in Both the Pantoyl and 

 /?-Alanyl Groups. A homologue of pantoyltaurine, DL-N-/3,8-dihydroxy- 

 7,y-dimethylvaleryltaurine (homopantoyltaurine) 15 is an antagonist of 

 pantothenic acid for Streptococcus hemolyticus with an inhibition index 

 of 20,000. 47 The inhibitory activity of this analogue is in contrast to that 

 of the corresponding ^-alanine derivative (homopantothenic acid). The 

 ^-alanine derivative exerts only a slight toxic effect, which is not reversed 

 by pantothenic acid. On the other hand, homopantoyltaurine is much less 

 effective than the corresponding pantoyl derivative (pantoyltaurine), 

 which inhibits growth at an index of 500. 



Another homologue of pantoyltaurine, N-ot,y-dihydroxy-/?,/?-dimethyl- 

 valeryltaurine (w-methylpantoyltaurine) , also has properties intermediate 

 between the corresponding y3-alanine and pantoyl derivatives. 73 w-Methyl- 

 pantoyltaurine inhibits competitively the utilization of pantothenic acid 

 in a large number of lactic acid bacteria as indicated in Table 33; how- 

 ever, it is much less effective than w-methylpantothenic acid, but is more 

 effective in some cases than pantoyltaurine. 



An unusual result was obtained with N-cc,y-dihydroxy-/?,/?-dimethyl- 

 valeryl-/?-aminobutyric acid, which prevents the growth of Escherichia 

 coli at a concentration of 100 y per cc. 91 The toxicity is prevented by 

 pantothenic acid. Usually analogues of pantothenic acid either do not 

 prevent the growth of organisms which synthesize the vitamin, or, if 

 growth is prevented at high concentrations, the toxicity is not prevented 

 by supplements of the vitamin. 



The activity of DL-N-a-hydroxy-/?,/?-dimethylbutyryltaurine, 14 which 

 prevents the utilization of pantothenic acid (inhibition index, 2000 for 

 half-maximum) or pantoic acid (inhibition index, 800 for half-maxi- 

 mum) by Acetobacter sub oxy dans, is in contrast with the corresponding 

 ^-alanine derivative, which possesses activity in replacing pantothenic 

 acid as a growth factor for this organism (cf. Table 24). 



N - ( y - Hydroxybutyryl) taurine and N 4 - (diacetylpantoyl) sulfanil- 

 amide have been reported to be antagonists of pantothenic acid for 

 Lactobacillus caseif® however, the former was found to have little 

 growth-inhibitory action with other organisms. 6S N-a,y-Dihydroxy-/3,/3- 

 dimethylvaleryl-L-leucine, 73 N- (/3-benzoylethyl) -a-hydroxycaproamide, 80 

 N- (£-benzoylethyl ) caproamide, 80 DL-N-a,y-dihydroxy-/?,/?-diphenyl- 



butyryltaurine, 60 DL-N-a-tosyl-y-hydroxy-y8,y3-dimethylbutyryltaurine, 60 



